Having read Adam Macqueen's commendably exhaustive encyclopaedia of Private Eye, the British satirical fortnightly, I now feel I know rather more about Lord Gnome's organ than I wish to. Still, this could be because I knew a fair bit about it to begin with, and Macqueen's book has only filled in the blanks. I've been with the Eye for nearly four of its five decades – I remember cutting out and pasting a cartoon clipped from its pages on to a school exercise book in 1972, when I was 12. As I recall it depicted Lord Longford – known for, among other things, his zealous campaign against pornography – walking past a couple of sniggering schoolboys, one of whom is whispering to the other, apropos of the bare-domed peer: "They say it makes you go bald." Needless to say, my teacher took a dim view of this decal, the creator of which I'm ashamed to say I can't remember, although it may have been the incomparable McLachlan, just one of the many great cartoonists to have found a home at the Eye over the years.

My pedagogues at secondary school also took a dim view of the Eye-inspired satire rag I photocopied and distributed, and which was named – in an homage to Dave Spart, their parody Trotskyite columnist – "The Alternative Voice". I don't think I got that close to being expelled for my shameless guying of teachers, revelations of their eccentricities and outright malfeasance, but it was made fairly clear that things would go badly for me if I didn't desist. What I'm trying to say is that the Eye and I have form, and when I grew big enough not simply to be a reader and emulator but also a target of its pasquinades, I confess I felt nothing but – as the late, lamented Peter Cook, the organ's one-time proprietor, would've put it, in character as Sir Arthur Streeb-Greebling – "stupefying pride". I have never, ever considered cancelling my subscription – to do so would be beyond infra dig.

To respond to a guying from the Eye is, as anyone in British public life should know, a very stupid thing to do, calling forth the well-attested-to "Curse of Gnome". Recipients of this inky-black spot include stellar egotists such as Piers Moron and Andrew "Brillo Pad" Neill (a deliberate misspelling of both their last names is rigorously enforced Eye house style); rampaging financiers such as the late Sir "Jams" Goldsmith and "Tiny" Rowland; press barons such as the Dirty Digger and the late "Cap'n Bob" Maxwell. Indeed, of the latter – who tried to snow the peskily truth-seeking Eye under with a blizzard of litigation during the early 90s, as his publishing empire sank into the murky waters of its own gross turpitude – it might almost be said that Lord Gnome stood behind him on the deck of his yacht and gave him a hefty shove. (That's enough Curse of Gnome, Ed.)

I make no apology for lacing this review with some of the in-jokes that Private Eye has established as its stock-in-trade during the past half-century. Frankly, if you're interested in the evolution of British politics and society and haven't at least a nodding acquaintance with the City commentary of "Slicker", the poetical works of EJ Thribb (aged 17-and-a-half), the agricultural updates of "Muckspreader", the architectural ones of "Piloti", the investigative journalism of the late Paul Foot – and the very much current Francis Wheen – and the parodies by Craig Brown, then you've no real business being here at all. Private Eye is, quite simply, as integral to British public life as the Times used to be – and this parallel is deeply instructive.

Founded in 1961 by a cabal of ex-public school boys – Christopher Booker, Richard Ingrams, Willie Rushton and Peter Usborne, who did their own mini-satire rags at Shrewsbury then Oxford before linking up with the nascent "satire boom" centred on Peter Cook's Soho Establishment Club – Private Eye has always had a deeply equivocal attitude towards the higher-ups it attempts to drag down. Macqueen quotes Ingrams quoting his own hero, William Cobbett, to explain the Eye's terms of engagement: "When [a man] once comes forward as a candidate for public admiration, esteem or compassion for his opinions, his principles, his motives, every act of his life, public or private, becomes the fair subject of public discussion." It's a purist satirical modus operandi, more pithily encapsulated by Ingrams as "get the shits".

But what it isn't, of course, is necessarily anti-establishment. On the contrary, with his brown corduroys and his general air of tweed-on-the-brain, Ingrams, who presided over the Eye for roughly half of its half-century, would seem the very epitome of a certain kind of English gentleman. His friend – and one-time "young fogey" – AN Wilson describes Ingrams as "deeply solipsistic", and having met him on a few occasions I can testify to his almost pathological reticence; but while he's inclined to style himself as an anarchist, what I suspect has always animated Ingrams is a desire not to destroy the state but purify it. And what infuriates him is not the exercise of power per se – let alone the existence of hierarchies and their ideologies of tradition – but the abuse of that power. He, like his successor Ian Hislop (also ex-public school and Oxford), is a regular Anglican communicant.

The Eye has thus always been a fairly broad church in terms of its political spectrum, stretching all the way from Foot's revolutionary socialism to Christopher Booker's flat-earth conservatism. But what all Eye-types evince – and Macqueen, who works there, is no exception – is a love of their own clique. Ingrams conceived of the Eye as "journalism done by a gang of friends", and since those friends shared the prejudices of their class-of-origin they were writ large over the years. Perhaps the most egregious example of this was the late Auberon Waugh. Defenders of his rather vicious attacks always pointed to their fantastical contextualisation as if this rendered them inert, but while personally Bron – as he was known – would never have been as crass as he was in print (and he did have redeeming features, including tireless campaigning for the victims of the Biafran war), he nonetheless exhibited all the de-haut-en-bas of his fictive alter-ego. I always suspected – and I knew him slightly – that his ill-repressed rage was actually a function of his status as the epigone's epigone. After all, it can never have been easy stepping into his father's shoes, Evelyn having been an incomparably greater misogynist, antisemite and homophobe.

To be fair to Hislop, in recent years the Eye has mostly been purged of its bigotry, while its record of speaking truth to power remains intact. To look back over the catalogue of its stories, from the Profumo scandal, to Deepcut, from T Dan Smith to Trafigura, is to turn back the pages of a book of wholly honourable revelation. That Private Eye shares many of the characteristics of the establishment it lampoons – male and Oxbridge-dominated – is perhaps inevitable, such is the way of a body politic that renews itself organically rather than through the violent purgation of regime change. However, there are signs that the Eye is in danger of becoming a less bilious organ and lapsing into the condition of an inert growth.

Hislop himself is a distinctly cosy figure, what with his heart-warming TV doccos and long-term residency at Have I Got News for You. He is also, I suspect, a fairly wealthy man, and while this in and of itself shouldn't put him in danger of full co-option as National Treasure, it puts him on the at-risk list. Then there are those in-jokes, which may have entered the lingua-franca of pol' speak in the Westminster village – and the wider world – but precisely because of that now seem like so much arcana. The joke-writing team at the Eye still defers to the arch-Oldies, while even Hislop and his writing partner Nick Newman have been at it for over a quarter-century. I seldom bother with the humorous pages of the Eye any more – nothing is that funny even twice, let alone 1,250 times.

But when all is said and done, while Private Eye may not be perfect, it's the only Private Eye we have, and for its unrivalled contribution to keeping the nation's candidates for public admiration on their toes, we should remain very grateful indeed.